The present invention relates to a process for producing difluoromethane and difluorochloromethane, which comprises fluorinating dichloromethane and trichloromethane with hydrogen fluoride in a liquid phase in the presence of a catalyst by one reaction apparatus.
It is known that difluoromethane (hereinafter referred to as xe2x80x9cHFC32xe2x80x9d) is produced by reacting dichloromethane (hereinafter referred to as xe2x80x9cHCC30xe2x80x9d) with hydrogen fluoride (hereinafter referred to as xe2x80x9cHFxe2x80x9d) in a gas or liquid phase in the presence of a catalyst.
U.S. Pat. Nos. 2,749,374 and 2,749,375 disclose that HCC30 is reacted with HF in a liquid phase at a temperature within the range from 110 to 175xc2x0 C. in the presence of an antimony chloride fluoride catalyst (SbClxFy, x+y=3,y/(x+y) greater than 0.8,Sb(V) greater than 5%) to give HFC32. In this process, however, a large amount of undesired monochloromethane (hereinafter referred to as xe2x80x9cHCC40xe2x80x9d) and fluoromethane (hereinafter referred to as xe2x80x9cHFC41xe2x80x9d), which are impurities other than HCC30 series and reduce the yield, are generated as by-products. It is also known that HF and antimony halide corrode a material of a reaction apparatus and it is extremely important in the production of HFC32 that the reaction system mixture does not corrode the material of the reaction apparatus. However, the above patents do not disclose that the material of a reactor shows the corrosion resistance in case of reacting under the above conditions. Furthermore, DE1,020,968 discloses that a reactor made of aluminum is used so as to establish the corrosion resistance.
U.S. Pat. No. 4,138,355 discloses that an equimolar amount of antimony trihalide is added to antimony pentahalide for a method for preventing the corrosion of the reactor by a halogen-containing organic compound such as a mixture of HF and antimony pentahalide. In this method, the catalyst is deteriorated with the progress of the reaction and the amount of antimony trihalide increases, which results in change of the catalyst composition. Therefore, it is necessary to cope with it.
Japanese Patent Kokai Publication No. 59-231030 (231030/1984) discloses a process wherein HCC30 is reacted with HF in a gas phase at a reaction temperature of 200xc2x0 C. by using aluminum fluoride or chromium fluoride as a catalyst to give HFC32. However, it can be said that this process is not an economically advantageous process because the reaction temperature is high (200xc2x0 C.) and this gas phase reaction requires a complicated apparatus in comparison with the liquid phase reaction.
As a process for producing difluorochloromethane (hereinafter referred to as xe2x80x9cHCFC22xe2x80x9d), a liquid phase synthesis process using trichloromethane (hereinafter referred to as xe2x80x9cHCC20xe2x80x9d) as a raw material is known (for example, U.S. Pat. Nos. 2,062,743 and 2,024,095).
An object of the present invention is to solve the above problems in the prior art, thereby providing a process of producing simultaneously or alternatively HFC32 and HCFC22 in an economical/safe manner in one reaction apparatus.
The present inventors have intensively studied various conditions of the process for producing HFC32 and HCFC22, which comprises fluorinating HCC30 and HCC20 with HF in a liquid phase in the presence of a catalyst. As a result, it has been found that there is a region where the respective production conditions are overlapped so that HFC32 and HCFC22 can be produced by using one reaction apparatus. Furthermore, the present inventors have studied the process for obtaining HFC32 and HCFC22 advantageously in view of economy and safety. Thus, the present invention has been accomplished.
The present invention provides a process for producing HFC32 and HCFC22, which comprises reacting HCC30 and HCC20 with HF in a liquid phase in the presence of a fluorinating catalyst in one reaction apparatus, wherein a reaction pressure is from 1 to 20 kg/cm2, and a reaction temperature is within the range from 50 to 150xc2x0 C. and is a temperature at which hydrogen fluoride is not liquefied under such reaction pressure.